Method of reclaiming the constituents from double base smokeless powder



, grains. vprovide a method for separating the nitrocellulose and United States Patent 2,843,584 .METHOD OF RECLAIMING TI-IE CONSTITUENTS FROM DOUBIJE BASE SMOKELESS POWDER IRobert Rood Buell, Prairie "du Sac, Wis., assignor to Liberty Powder Defense Corporation, Baraboo, WlS., a corporation of Delaware No Drawing. Application March 7, 1955 Serial -No. 49z','770

6 Claims. (Cl. 260-223) a base for making globular grains of acceptable stability.

One method for recovering thenitrocellulose from single base smokeless powder grains is disclosed in U. S. 2,642,350, issued June 16, 1953, to D. A. Aldersonet 211.

'It has not been possible heretofore, however, to reclaim the explosive constituents of double base smokeless "pow- 'ders, i. e., powder grains containing a liquid explosive nitric ester in addition to nitrocellulose, because no suitable method has been available for recovering the liquid explosive nitric ester in a form suitable for use in the formation of new powder grains. 7

It is therefore an object of this invention to provide a novel process for reworking double base smokeless powders. Another object of this invention is toprovide a method for reclaiming the nitrocellulose and the liquid explosive nitric ester'from double base powder grains in aform suitable for use in the manufacture -"of'new powder A more .specific object of this invention is to the liquid explosive nitric ester in smokeless powder grains 'from each other and from "the other ingredients of such grains in a form suitable .for .use in the m'anufiacture of v globular powder grains.

Generally speaking, the objects of this inventionare accomplished by extracting double base smoke'less powder grains with a non-solvent for nitrocellulose which is a solvent for the liquid explosivenitric ester, the stabilizers and modifiers in the smokeless'po'wder grain and thereafter contacting the solvent phase with an adsorbent for the stabilizers and modifiers. 'The inventionis predicated upon the discovery that the stabilizers =and modifiers of the burning characteristics of smokeless powder which are utilized in double base smokeless powder :grains such as, for example, methyl centralite, ethyl centralite, triacetin, dibutyl phthalate, di-ethyl phthalateand the like and the liquid explosive :nitric esters utilized in making double base powders such as, forexample, nitroglycerin and the nitroglycols and the like can be selectively dissolved "from the nitrocellulose of a: smokeless powder grain in a solvent having a low dipole momentand the liquid explosive nitric ester can thereafter be. recovered as the solute in the solvent from the stabilizers and modifiers by adsorbing them on particles of silicic acid or other suitable specific adsorptive agent.

The particular solvent of the-class provided by this thereof:

invention which is best suited for extracting the liquid explosive nitric ester and the stabilizers and modifiers from the nitrocellulose of a particular smokeless powder is dependent upon the solubility of the various modifiers, stabilizers, and other ingredients of the graintherein and its relative affinity for the stabilizers and modifiers when compared to that of silicic acid. The solvent also must be non-reactive with nitrocellulose and other ingredients of the smokeless powder grains. In orderto facilitate separation of the solvent from the nitrocellulose in the extraction process, it is preferred to use a volatile solvent having a boiling point less than that of water. Examples of solvents suitablev for the purpose are xylene, toluene, and benzene but the first two because of their boiling point and greater polarity are less desirable commercially than the latter. Similarly, aliphatic hydrocarbons or mixtures thereof such as ligroin because of their low dipole moment are also suitable solvents for use as the extractor. Materials such as 'cyclohex ane and acetone, on the other hand, are unsuitable because of the solubility of nitrocellulose therein.

Benzol has been found especially advantageous for use as an extractor of double base powder grains 'containing nitrocellulose, nitroglycerin, diethyl phthalate and ethyl centralite. Each of these ingredients except the nitrocellulose is soluble in benzoland it has been found that a solution of the same can be separated from the nitrocellulose. The benzol containing nitroglycerin, die'thyl phtha'la'te and ethyl c'entralite as solutes is then passed through an adsorption column containing particles 'ofsili'cic acid which adsorbs the diethyl phthalate and ethyl centralite leaving the nitroglycerin as a solute in the benzol which emerges from the column. When the adsorbent in the extracting column becomes saturated with centralite andxdiethyl phthal'ateand the latter materials are detected in the solution emerging from the column, extraction is stopped and the siiici'c acid is regenerated by fiowin'g through the column a-quantity of ethyl ether which elutes the adsorbent compounds and carries them from the column. and the column is ready for additional extractionsof powder grains.

.In order further to describe and clarify the invention the following is'a' detail description of one embodiment The contents of the tank are heated to about 55 C. and

agitated for from about 3 to 6 hours or until the extraction equilibrium has been reached. The liquid phase is separated from the solids by permitting-it to flow'from the bottom of the tank through a suitable screen or filtering medium and an inert gas such as nitrogen is blown through the powder bed to remove the last traces of benzol. The-benzol is condensed and recovered for use in further extractions andthe nitrocellulose remaining in the tank is suitable foruse in making smokeless powder grains;

The benzol drawn centralite as a solute therein is transfer-red to "an ad- .sorption column containing a mixture'of about twolp arts granular 'silicic acid per one part diatomaeeous earth such as, for :examplmthe commercial product sold under the trade name .Celite 53 '5.f" This particular material The ether is ,then replaced with fresh benzol from the powder grainsand containing the nitroglycerin, diethyl phthalate, fandfethylsure is reduced to about 300 millimeters mercury and the contents of the still are heated to the boiling point which is about 45 C. As distillation progresses the temperature gradually increases to about 55 C. and is held at this point until all of the benzol has been distilled. The water layer in the still is then separated from the nitroglycerin by drawing it ofi from the bottom of the still and about 97 to 98 parts by weight ethyl acetate per 100 parts by weight nitroglycerin are pumped into the tank containing the nitroglycerin. This mixture is agitated together until the mixture has reached equilibrium. Agitation is then stopped and the contents of the still separates into two layers. The nitroglycerinethyl acetate solution is drawn out of the tank to separate it from the water layer. The nitroglycerin-ethyl acetate solution is suitable for use in coating globular powder grains with nitroglycerin in accordance with the process disclosed in U. S. Patent 2,213,255.

When the silicic acid becomes substantially saturated with diethyl phthalate and ethyl centralite, it is regenerated with ethyl ether. Regeneration is achieved by filling the column with ethyl ether and dissolving the diethyl phthalate and ethyl centralite adsorbed on the particles of silicic acid. The resulting solution is removed from the column and benzol is pumped through the column to replace any ethyl ether remaining therein.

The column is then in condition for further adsorption of the compounds from a benzol-nitroglycerin solution.

In the foregoing example, the silicic acid used was of such a granulation that it had a bulk density of about 50 fluid ounces per pound and an average particle size of 0.05 micron. These particles have a tendency to become aggregated into particles of about 30 microns. This particular granulation has been found well suited for the adsorption column but any other suitable granulation can be utilized. it should be borne in mind, however, that the finer the particle size the more efficient the adsorption per unit area of column. Celite 535 or other diatomaceous earth is combined with the silicic acid in order to facilitate flow of the solution through the column. It is not absolutely essential that such a material be included with the silicic acid but it is advantageous in practice. Other materials similar to a diatomaceous earth can be used as packing for the column in lieu of Celite and the relative amounts of adsorbent and diatomaceous earth can vary over wide ranges depending upon the column used and the granulation of packing materials.

in practice it is advantageous to recycle the solvent and thus use it for extracting more than one batch of powder before passing it through the adsorption column to separate the liquid explosive nitric ester from the other solutes therein. For best results, however, it is advisable to arrange for the last solvent used to be substantially pure in order to remove the maximum amount of liquid explosive nitric ester and other materials soluble in the solvent from the nitrocellulose. In one arrangement found particularly advantageous, double base smokeless powder grains are extracted first with solvent which has been used previously for extracting two other batches of powder. This extraction is followed with one using solvent which has been previously used for extracting only one batch of powder. Then the final extraction is made with substantially pure solvent.

If the amount of liquid explosive nitric esters, stabilizers, and modifiers is relatively low in a double base powder it is obvious that less solvent therefor will be required in the extraction. Moreover, it may not be necessary to remove the total amount of these materials from the powder grain if the globular powder to be manufactured therefrom contains some of these materials. lf this type of powder is to be made from the scrap powder and it is desired to incorporate the nitroglycerin in the grain it is only necessary to extract that amount in the waste powder which is in excess of that desired in the finished product. Ordinarily, however, globular powder grains are coated with the nitroglycerin and it is undesirable to include it in the grain so substantially complete extraction of the nitroglycerin is usually required.

Although the invention has been described in detail in the foregoing it is to be understood that many variations can be made by those skilled in the art without departing from the spirit of the invention or the scope thereof except as limited by the appended claims.

1 claim:

1. A method for reclaiming nitroglycerin and nitrocellulose from double base smokeless powder grains which comprises mixing the powder grains with a solvent for the nitroglycerin which is a non-solvent for the nitrocellulose, separating the solvent phase from the undissolved nitrocellulose contained in said powder grains and contacting it with silicic acid.

2. A method for recovering nitrocellulose and liquid explosive nitric esters selected from the group consisting of nitroglycerin and nitroglycols from double base smokeless powder grains which comprises extracting the powder grains with a solvent for the nitric esters which is a non solvent for nitrocellulose, separating the solvent phase from the undissolved nitrocellulose contained in said powder grains and contacting the solvent phase with particles of silicic acid.

3. A method for reclaiming nitrocellulose and nitroglycerin from smokeless powder which comprises extracting the nitroglycerin from the powder grains with benzol, separating the benzol phase from the undissolved nitrocellulose contained in said grains, and thereafter contacting the benzol phase with particles of silicic acid.

4. A method for segregating nitrocellulose and liquid explosive nitric esters selected from the group consisting of nitroglycerin and nitroglycols from double base smokeless powder comprising extracting the powder with a nonsolvent for nitrocellulose that is a solvent for the liquid explosive nitric ester, separating the solvent phase from the insoluble nitrocellulose, contacting the solvent phase with particles of silicic acid, and thereafter separating the liquid explosive nitric ester from its solvent.

5. A method for recovering nitrocellulose and nitroglycerin from smokeless powder grains containing the same and also containing ethyl centralite and diethylphthalate which. comprises dissolving the nitroglycerin, diethylphthalate and ethyl centralite in a benzol solution, separating the solvent phase from the undissolved nitrocellulose, adsorbing the diethylphthalate and ethyl centralite from the solvent phase with silicic acid and subsequently separating the nitroglycerin from the benzol.

6. The method of claim 5 in which the solvent is benzol.

References Cited in the file of this patent UNITED STATES PATENTS 1,593,254 Prutzman et al. Aug. 31, 1926 1,653,519 Speicher Dec. 20, 192 1,992,979 VVollner Mar. 5, 1935 2,280,812 Ellis Apr. 28, 1942 2,642,350 Alderson et al. June 16, 1953 2,728,715 Rampino Dec. 27, 1955 FOREIGN PATENTS 245,078 Great Britain June 3, 1926 

1. A METHOD FOR RECLAIMING NITROGLYCERIN AND NITROCELLULOSE FROM DOUBLE BASE SMOKELESS POWDER GRAINS WHICH COMPRISES MIXING THE POWDER GRAINS WITH A SOLVENT FOR THE NITROGLYCERIN WHICH IS A NON-SOLVENT FOR THE NITROCELLULOSE, SEPARATING THE SOLVENT PHASE FROM THE UNDISSOLVED NITROCELLULOSE CONTAINED IN SAID POWDER GRAINS AND CONTACTING IT WITH SILICIC ACID. 